Hybrid optical delivery system for photoplethysmography

Abstract

A hybrid optical system for photoplethysmographic measurements is disclosed. The system delivers light from a plurality of emitters to the tissue-under-test. A set of one or more of the emitters resides in close proximity to the sensor. A second set of one or more emitters resides at some distance from the sensor with the light from this second set of emitters being delivered to the sensor by a light pipe typically consisting of a fiber optic cable. This invention allows the photoplethysmographic instrument designer to use two or more different types of emitters in the same photoplethysmographic device while still generating a technically feasible and cost effective design.

What is claimed is:  
     
       1. A photoplethysmographic measurement apparatus for measuring one or more blood analyte levels or one or more hemodynamic parameters in a tissue-under-test, comprising: 
       a plurality of separate emitters, wherein each emitter produces a light signal having a unique spectral content, said emitters separated into two sets of at least one emitter each;  
       a sensor which makes direct contact with the tissue-under-test and provides an output aperture through which light signals are delivered to the tissue-under-test;  
       housing means for housing each of the two sets of emitters in two separate locations, said housing means comprising a first housing means located proximal to said sensor and a second housing means located some distance from said first housing means;  
       means for transporting said light signals from said first and said second housing means to said sensor;  
       means for guiding the light signals from said first and second housing means through said output aperture to be incident on the tissue-under-test;  
       means for receiving a portion of the light signal exiting the tissue-under-test and converting said received light-signal to an electronic signal indicative of the said received light signal;  
       means for processing said received light signal to determine one or more blood analyte levels or one or more hemodynamic parameters.  
     
     
       2. The apparatus as claimed in  claim 1  wherein said sensor provides the opto-mechanical means to co-locate all of the said output light signals to pass through said output aperture to be incident upon the tissue-under-test. 
     
     
       3. The apparatus as claimed in  claim 2  wherein said first housing means resides in said sensor immediately proximal to the tissue-under-test. 
     
     
       4. The apparatus as claimed in  claim 2  wherein said first housing means is located inside a connector that is removably attached to said sensor. 
     
     
       5. The apparatus as claimed in  claim 3  wherein said first housing means is permanently attached to said sensor. 
     
     
       6. The apparatus as claimed in  claim 2  wherein said two sets of emitters are of distinctly different types of optical sources. 
     
     
       7. The apparatus as claimed in  claim 6  wherein at least one set of said emitters consists of a plurality of one or more light emitting diodes. 
     
     
       8. The apparatus as claimed in  claim 6  wherein at least one set of said emitters consists of a plurality of one or more laser diodes. 
     
     
       9. The apparatus as claimed in  claim 2  wherein said means for transporting said light signals from said emitters in said second said housing means to said sensor includes one or more of the following group comprising, optical fibers, an optical fiber bundle, plastic fiber, and a single liquid core guide. 
     
     
       10. The apparatus as claimed in  claim 2  wherein said blood analyte levels consists of the measurements of the percentages of oxyhemoglobin, carboxyhemoglobin, methemoglobin and reduced hemoglobin in the arterial blood. 
     
     
       11. A photoplethysmographic measurement apparatus for measuring the concentrations of a plurality of blood analytes, in a tissue-under-test, comprising: 
       a plurality of light emitters, said emitters separated into two sets of at least one emitter each;  
       a sensor which makes direct contact with the tissue-under-test and provides an output aperture through which light signals are delivered to the tissue-under-test;  
       a photo-detector which receives a portion of the remaining light signal output from the tissue-under-test and converts said light signal to an electronic signal indicative of said light signal incident on the photo-detector;  
       a processing means which converts said electronic signal into blood analyte levels wherein said blood analytes includes at least two of the group comprising: oxyhemoglobin, carboxyhemoglobin, methemoglobin, reduced hemoglobin, and reduced hemoglobin;  
       an output means that generates a user readable output of said blood analyte levels;  
       housing means for housing each of the said two sets of emitters in two separate locations, said housing means comprising a first housing means located proximal to said sensor and a second housing means located some distance from said sensor;  
       means for transporting said light signals from said second said housing means to said sensor;  
       means for guiding all of said light signals through said output aperture.  
     
     
       12. An apparatus as claimed in  claim 11  wherein each emitter produces a light signal having a unique spectral content. 
     
     
       13. In a photoplethysmographic measurement system, a method for measuring one or more blood analyte levels or one or more hemodynamic parameters in a tissue-under-test, said method comprising the steps of: 
       providing a plurality of separate emitters, wherein each emitter produces a light signal having a unique spectral content, said emitters separated into two sets of at least one emitter each;  
       providing a sensor which makes direct contact with the tissue-under-test and providing an output aperture through which light signals are delivered to the tissue-under-test;  
       providing a housing means for housing each of the two sets of emitters in two separate locations, said housing means comprising a first housing means located proximal to said sensor and a second housing means located some distance from said first housing means;  
       providing a means for transporting said light signals from said first and said second housing means to said sensor;  
       guiding the light signals from said first and second housing means through said output aperture to be incident on the tissue-under-test;  
       providing a means for receiving a portion of the light signal exiting the tissue-under-test and converting said received light signal to an electronic signal indicative of the said received light signal;  
       processing said received light signal to determine one or more blood analyte levels or one or more hemodynamic parameters.  
     
     
       14. The method of  claim 13  further comprising the step of: 
       substantially co-locating all of said output light signals to pass through said output aperture to be incident upon the tissue-under-test.  
     
     
       15. The method of  claim 14  further comprising the step of: 
       positioning said first housing means to reside in the sensor immediately proximal to the tissue-under-test.  
     
     
       16. The method of  claim 14  further comprising the step of: 
       positioning said first housing means inside a connector that is removably attached to said sensor.  
     
     
       17. The method of  claim 15  further comprising the step of: 
       positioning said first housing means permanently attached to said sensor.  
     
     
       18. The method of  claim 14  further comprising the step of: 
       including said two sets of emitters wherein the said sets contain emitters consisting of distinctly different types of optical sources.  
     
     
       19. The method of  claim 18  further comprising the step of: 
       including a plurality of one or more light emitting diodes in at least one set of said emitters.  
     
     
       20. The method of  claim 18  further comprising the step of: 
       including a plurality of one or more laser diodes in at least one set of said emitters.  
     
     
       21. The method of  claim 14  further comprising the step of: 
       transporting said light signals from said emitters in said second said housing means to said sensor using one or more of the following group comprising, optical fibers, an optical fiber bundle, plastic fiber, and a single liquid core guide.  
     
     
       22. The method of  claim 14  further comprising the step of: 
       measuring said blood analyte levels including the measurements of the percentages of oxyhemoglobin, carboxyhemoglobin, methemoglobin and reduced hemoglobin in the arterial blood.